This document provides an overview of the switch virtual interface (SVI) for Cisco® Integrated Services Routers.
Cisco offers different flavors of integrated switching modules for the modular Cisco 3900, 3800, 2900, 2800, 1900 and 1800 Series Integrated Services Routers: the Cisco 4- and 8-Port Gigabit Ethernet Enhanced High-Speed WAN Interface Cards (EHWICs), 16- and 36-port Cisco EtherSwitch® modules, the Cisco EtherSwitch 4- and 9-port high-speed WAN interface cards (HWICs), the Cisco EtherSwitch service modules, and the Enhanced Cisco EtherSwitch service modules. In addition, the Cisco 1800 and 890 Series fixed-configuration Integrated Services Routers are integrated with an 8-port switch. The Cisco 880, 870, 860 and 850 Series Integrated Services Routers are integrated with a 4-port switch.
The integrated switch ports for the fixed-configuration Integrated Services Routers and the switch ports on the HWICs/EHWICs do not natively support Layer 3 addresses or Layer 3 features. They must be assigned to a SVI and use a VLAN interface for Layer 3 features. SVI represents a logical Layer 3 interface on a switch. In addition to basic routing, SVI can be used to support additional features for the network that the SVI represents.
Table 1 lists the Cisco IOS® Software features supported by SVI and summarized the typical use of these features. Please refer to the Feature Navigator Tool to check whether a specific platform supports a specific feature.
Table 1. Cisco IOS Software Features Supported by SVI
Cisco IOS Software Feature
SVI Use Scenario
SVI Support Status
Routing Features
Routing protocols
Interconnects Layer 3 networks using protocols such as Routing Information Protocol (RIP), Open Shortest Path First (OSPF) Protocol, and Enhanced Interior Gateway Routing Protocol (EIGRP) configured under SVI
Yes
IP Version 6 (IPv6)
Provides IPv6 support
Yes
Network Address Translation (NAT)
Translates public IP addresses to private address pools, and private addresses to public IP addresses; SVI is typically used as a NAT inside interface
Yes
Dynamic Host Configuration Protocol (DHCP)
• DHCP server feature: Dynamically assigns private IP addresses to devices connected to the switch ports
• DHCP client feature: Allows the SVI to receive a dynamically assigned IP address
Yes
Hot Standby Routing Protocol (HSRP)
Supports redundancy and high availability with a secondary device connected to the LAN with SVI, using HSRP
Yes
Virtual Router Redundancy Protocol (VRRP)
Supports redundancy and high availability with a secondary device connected to the LAN with SVI, using VRRP
Yes
Gateway Load Balancing Protocol (GLBP)
Supports redundancy and high availability with a secondary device connected to the LAN with SVI, using GLBP
No
Policy-Based Routing (PBR)
Creates policy maps for routing decisions and QoS settings
Yes
Point-to-Point Protocol (PPP) over Ethernet (PPPoE)
Provides PPPoE client support for a device (such as a DSL modem) connected to the switch port; typically used when the SVI is the only interface available to provide backup using the external device
Yes
Multicast
Provides multicast support for clients connected to the switch ports
Yes
VPN Routing and Forwarding (VRF)
Associates a VRF instance with an SVI to map VLANs to different logical or physical VPN WAN connections
Yes
Layer 2 Tunnel Protocol Version 3 (L2TPv3)
Provides LAN extension between remote sites; SVI is used as the Layer 2 tunnel termination point
Yes (12.4(20)T or later)
Ethernet over MPLS (EoMPLS)
Provides Ethernet extension between remote sites; SVI interface used as the EoMPLS pseudowire attachment circuit
Yes(15.2(2)T or later)
Security Features
IP Security (IPsec)
• Supports Easy VPN remote as the inside interface
• Provides IPsec tunnel termination on the SVI; typically used when SVI is the only interface available to provide backup WAN connection with an external device (such as a DSL modem)
Yes
Generic Routing Encapsulation (GRE)
Provides GRE tunnel termination on the SVI;, typically used when SVI is the only interface available to provide backup WAN connection with an external device (such as a DSL modem)
Yes
Firewall
Provides Firewall support for VLANs
Yes*
Intrusion Prevention System (IPS)
Provides IPS support for VLANs
Yes
IP access control lists (ACLs)
Provides packet filtering to control network traffic and restrict the access of users and devices to the network
Yes
Network Admission Control (NAC)
Enforces NAC of endpoint devices connected to the VLAN
Yes
Auth-proxy
Authenticates inbound and outbound users connected to the VLAN
Yes
Quality-of-Service (QoS) Features
Classification with standard and extended access list
Provides QoS classification with standard and extended access lists
Yes (CSCsi01713)
Classification with IP type of service (ToS): IP precedence, differentiated services code point (DSCP), or destination address
Provides QoS classification with IP ToS bits
Yes
Classification with Network-Based Application Recognition (NBAR) with TCP
Provides QoS classification with NBAR TCP traffic
Yes
Class-based marking
Provides QoS marking based on user-defined traffic class with DSCP and IP precedence values
Yes
Policing
Limits the input or output transmission rate on SVI and specifies traffic handling policies when the traffic either conforms to or exceeds the specified rate limits
Yes (15.1(1)T or later)
Committed Access Rate
Limits the input or output transmission rate on SVI
Yes
Class-Based Traffic Shaping
Provides Generic Traffic Shaping based on user defined traffic class
No
Generic-Traffic Shaping
Limits the transmission rate of data to match the speed of the remote, target interface and helps ensure that the traffic conforms to policies contracted for it
No
Weighted Random Early Detection (WRED)
Provides early detection of congestion and differentiated performance characteristics for different classes of service
No
Class-Based Weighted Fair Queue (CBWFQ)
Allocates bandwidth based on user-defined traffic class
No
Low-Latency Queue (LLQ)
Provides strict priority queuing with CBWFQ to allow delay-sensitive data such as voice to be dequeued and sent first, giving delay-sensitive data preferential treatment over other traffic
No
Hierarchical QoS
Using a modular QoS command-line interface (CLI) in a hierarchical structure, provides a high degree of granularity for QoS policies and helps meet complex service-level agreement (SLA) requirements
No
* Transparent Firewall is only supported between a VLAN and WAN interfaces. It's not supported between 2 or more VLANs. Please refer to CSCse92575.
Conclusion
SVI on Cisco Integrated Services Routers is designed to provide basic Layer 3 functions for the Layer 2 switch ports that belong to a specific VLAN. The SVI does not provide the same feature set and functions as the integrated Layer 3 Ethernet ports of the integrated services routers and should not be used to entirely replace the Layer 3 Ethernet ports. Customer who need additional Layer 3 Ethernet ports for their Integrated Services Routers may consider the use of 1- and 2-Port Fast Ethernet High-Speed WIC for modular ISR platforms. The guidelines presented in this document summarize feature support considerations for an Integrated Services Router deployment that uses SVIs.
For More Information
Please refer to the following links for more information:
• Cisco 4- and 8-Port Gigabit Ethernet Enhanced High-Speed WAN Interface Cards:
Cisco Router and Security Device Manager (SDM) is installed on this device.
This feature requires the one-time use of the username "cisco" with the password "cisco". The default username and password have a privilege level of 15.
Please change these publicly known initial credentials using SDM or the IOS CLI.